Toggle latches have evolved over many years. Individual design fasteners have derived from the constantly developed improvements, such as toggle latches generally known as the under-center type. This type of latch has been disclosed recently in U.S. Pat. No. 3,127,205. The general configuration of this type of latch makes it adaptable for use in more confined areas since it requires less space to work in than the typical type of over-center toggle latches.
In general, whether the latch is over-center or under-center in operation, the latching action is achieved through an interengagement between a drawbar and a keeper element and then shifting of a lever to move the interpivoted drawbar axially into tight interengagement with the keeper element. During the action of latching the movable pivot connecting the lever arm with the toggle bar is shifted to a position where it is over or under-center with respect to a fixed pivot so that any tendency to move the drawbar toward the keeper element is restricted by the mounting of the assembly in combination with the over or under-center movable pivot position whereby the drawbar tends to restrict itself from axial movement to the unlatched position.
In general, there is minimal tolerance permitted between the interengaging elements of the toggle latch. If the drawbar and interconnected lever assembly is not properly positioned with respect to the keeper element, the latching action could be incomplete if they are spaced incorrectly in one direction or impossible if they are spaced incorrectly in an opposite direction. Consequently, various improvements have been derived which permit adjustment of the toggle latch assembly and the keeper element so that the proper latching action can occur. In many cases these improvements are cumbersome and time-consuming to operate and their complexity often leads to an expensive and inefficient product to manufacture. In fact, in view of the complexity of the varied components of the assembly, an improvement regarding simplicity of construction would be advantageous from a cost standpoint.
It should also be kept in mind that while wide tolerances are desirable for mass production and operation of the toggle latches, it is imperative that the latch be positive and rigid in its locking action so that the members interengaged are retained in tight interengagement during use. Consequently, loose fits or components having wide tolerances could detract from positive locking action and result in a less than desirable latching action.
In conclusion, as has been exemplified by the development of the state of the art over many years, constant improvement and development continues in order to improve the versatility of available types of toggle latches as well as improving their simplicity of operation to minimize the space required for mounting and use of the latches to lower the cost of construction thereby providing a more economic latch, and to increase the workable tolerances of the resultant product while retaining the rigid positive latching effect. Of course, it is also valuable to maintain the strength of the latch at the most desirable level to enhance its areas of applicability.